Heating-unit terminal



A. D. KEENE HEATING UNIT TERMINAL April 12 1927. 1,624,345

Filed March 26, 1925 A/i//h DL/eene BY M Patented Apr` l2, 192,7.

UNITED STATE-s- 1,624,345 PATENT oFFiCE.

ALVIN D. KEENE, F' PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE 4ELECTRIC & MANUFACTURING COMPANY, A CORPORATION 0F PENNSYLVANIA.

HEATING-UNIT TERMINAL.

Application filed March 26, 1925`. Serial No. 18,424.

Wy invention relates to electric heating units and particularly to terminal members therefor.

An object of my invention is to provide a relatively simple and easily manufactured terminal member for an embedded heating unit. f

ln practicing my invention, I provide a resistor member` of substantially non-oxil dizable materiaLlhat has its end portion wrapped around the end of a rod or bar of non-oxidizable material, a wire of iron or steel being interposed between the adjacent turns ot' the resistor wire on the rod. ln the single sheet of drawings, Figure 1 is a fragmentarywiew, in side elevation, of a device embodyingr my invention,

Fig. 2 is a view in longitudinal section 2" through a device embodying my invention,

and

Fig. 3'is a view, in longitudinal section, through a modified form of device embodying my invention. y

An improved terminal device embodying my invention is particularly applicable to, and may be etiectively used with, `an embedded heating element of the kinddisclosed and claimed in my copending appli-- cation, Serial No. 18.42.73; filed i\'larch QG, 1925 which is assigned to the \\"estinghouse Electric & Mfg. Company.

'lhe heating unit comprises a resistor wire 11 of any suitable or desired size and length i5 that is preferably wound into substantially helical form. If a heating unit ot substantially rectangular form is to be made, the helicallywound resistor member 11 is so sha )ed as to provide a plurality of substan- 0 tially parallel-extending, spaced, straight convolutions, the entirele'ngth of lthe resistor wire is covered with a layer of initially-moistened, comminuted material, such as alundum, which is permitted to dry there- 5 on. The formed and insulated resistor Wire is then embedded in a mass of heat-and-electricconducting comminuted material, such as carborundum, Awhich is tightly compressed to form' a flat heating unit.

f If a heating,r `unit of rod form is to be `Constructed, the` resistor member 11 need not be insulated with a layer of electricinsulating material, and is simply embedded in .a mass 120i heat and electric conducting material, such as carborundum, that is initially in moistened and comminuted form and that mayy have mixed therewith a small quantity of clay that acts as a binder. .The mass 12 of carborundum is tightly compressed around the resistor wire and the end of a terminal bar, 13, that projects into the mass 12, substantially as illustreated in Fig. 1 of the drawing.

The bar or rod 13, which may be of circular or of rectangular shape in lateral section, has the end ot' the resistor wire 11 wound therearounda predetermined number of times and is covered with a layer 14 of initially moistened comminuted'electricinsulating-material, such as alundum. A

relativelysmall iron or steel wire 15 is also wrapped around the inner end of therod or bar 13 substantially as illustrated in Fig.v 2 of the drawing. The wire" 11, which is usually of nichrome, may be. wrappedI tightly around the inner` end of the rod 13, together' with the interposed wire l'and the turns will be held tightlyl against the bar 13, in substantially the position illustrated in Fig. 2 oi' the drawing, particularly when the mass 12 of silicon carbide, commonly known as rarborundum, has been compressed at relatively high pressures around the resistor member and the terminal member. v Y

In order to thoroughly dry out the mass 12, it is necessary to heat the same to a relatively high temperature and the 'initial subjection of the wire 15, which is made of steel or iron, to heat, causes a change in the crystalline structure thereof, and an accompanying transformationA thereof into an oxide which is a very good conductor of electricity. Simultaneously with the change in crystalline structure and the transforma- .tion into an oxide, the Wire 15 swells or increases in lateral area and, generally, in volume, thereby ei'ecting a wedging action between the outer surface of `the bar 13 and that part of the turns of the wire 11 directly operatively engaged by the Wire 15, and providing a good electrical contact and currentconducting portion therebetween.

As the Wire 11 and the rod 13 are of nichrome, which isl of relatively non-oxidizable material relatively little change, if any, will take place during this heating or during the heating that is etiected by operating such a heating unit.

Fig.l 3 illustrates a modified form of terminal member in which a rod or bar 16 is provided with a reduced inner portion 17 having an end shoulder portion 18, the Wire 11 being wound a predetermined number of times around the reduced portion between the two shoulders provided thereby.

A Wire 19, of iron or steel, iswound between the turns, which are here shown as slightly spaced from one another and substantially the same action, or change in crysf4 talline structure, and a transformation into a conducting oxide and a Wedging action, is effected upon the initial heating of the device.

As the transformed wire members l and 19 do not lose their originallyV acquired greater volume, the Wedging action is a continuous one and, if, anything, is improved in the course of repeated heating by reason of the normal operation of the device.

Various modifications and changes may be made Without departing from the spirit and scope of the invention, and I desire, therefore,fthat only such limitations shall be placed thereon as are imposed by the prior art.

I' claim as my invent/ion:

1. A terminal member for an electric heating element having a substantially non-oxi dizable Wire, comprising a substantially non-oxidizable member, having a plurality ot' turns ot the substantially non-oxidizable wire wrapped therearound, and a plurality ot' turns of wire of an oxidizable material disposed around said non-oxidizable member intermediate the turns of said substantially non-oxidizable wire.

' Q. A terminal membertor an electric heating element having a substantially non-oxidizable Wire, comprising a substantially non-oxidizable member having a plurality ot turns ot the non-oxidizable Wire wrapped tlierezuound,y and means, operatively engaging said Wire and said substantially nonoxidizable member, that expands permanently upon being heated and provides an electric conducting path between the two members. i

3. A terminal member for an electric heating" element having a substantially non-oxidizable Wire resistor, comprising an elongated member of substantially non-oxidizable material, said member having a pair of spaced shoulders thereon and a plurality of turns ot theresistor wire wrapped there- 'around between said shoulders, and a plurality of turns of a wire of oxidizyable material wound around said elongated member between-said shoulders and engaging said wire and said elongated member, said oxidizable Wire swelling permanently upon be ing heated and Wedging said turns of resistor wire tightly between said shoulders. l

4. A'terminal member foran embedded heating element having a resistor wire of substantially non-oxidizable material insulatedly mounted in a layer of compressed heat-ancl-electric-conducting material, comprising an elongated member, of substantially nonoxidizable material, having a portion extending into said layer of material and having a plurality of turns ot the resistor Wire Wrapped therearound, a plurality of turns of wire of a material that .swells permanently upon being heated, Wrapped around said elongated. member intermediate the turns ot the resistor Wire, anda coating of powdered, electric-insulating material around the embedded portion of the elongated member and the wire Wrappings thereon.

In testimony whereof, I have hereunto subscribed my name this 13th day of March, 1925.

ALVIN D. KEENE. 

